Electrical scanning



INVENTOR ord,

ATTORNEY April4 13, 1954 A. v. BEDFORD ELECTRICAL SCANNING 2 Sheets-Sheet 2 Filed April l, 1950 RN w Patented Apr. 13, 1954 ELECTRICAL scANNING Alda V. Bedford, Princeton, N. J., assignor to Radio Corporation of America, Princeton, N. J., a corporation of Delaware Application April 1, 1?:30, Serial No. 153,473

19 Claims. (Cl. TIS-5.4)

The present invention relates to electrical scanning methods and systems and more particularly, although not necessarily exclusively, to scanning systems and methods used in the color television representation of images or scenes.

More directly, the present invention is involved with improved methods, techniques and apparatus for generating color television signals of the type used to delineate a number of primary color images which, when superimposed, produce a television image having full color.

Various ways are presently known to produce color television images. In practically all of the more popular systems, the scene to be televised in color is eiiectively scanned by a number of television cameras all at the same time. Each camera is fixed to pick up only one particular color aspect of the picture. The colors assigned to each of the cameras scanning the scene are chosen so that they are additively complementary. That is to say, when all the colors represented by the cameras are added together, they will produce white light.

Present trends point to the use of only three television cameras or, more generally speaking,

three complementary color records of a given scene. The color represented by each of the complementary color records is referred to as a primary color and as above noted, these three primary colors must add together to produce white light. It is noted that other systems using only two primary colors are possible, while color fidelity is improved if more than three color records are used. Nevertheless, most present-day color television transmission systems are based upon only three primary colors, usually red, green and blue.

1f three separate cameras are used to scan the same scene and each camera represents a separate primary color aspect of the scene, extreme care must be used in registering the cameras. If the scanning actions of all three camerasare not exactly timed with one another, it is apparent that the three color images reproduced at the receiver by aid of the cameras will not exactly register when superimposed. The bad effects of improper registration will be most noticeable in connection with the picture detail of the reproduced color television image. This makes the picture look blurred even though each of the individual primary color images produced by the cameras ,may be very clear.

When using separate television cameras to produce separate color records of a scene, another problem arises. This problem is the light loss contributed by the color iilters placed in front of each of the cameras. For instance, i1 ordinary panchromatic or black and white type television cameras are used .in a color television system, it

has, in the past, been the practice to put a diiferent color iilter in iront of each camera. The red camera wouldhave a red lter. The blue camera would have a blue filter and, of course. the green camera would be provided with a green filter. Since most television cameras generate Within themselves a certain spurious signal output regardless of whether they see light or not, the use of the filter tends to decrease the signal-tonoise ratio of the system. For instance, the blue iilter in front of its camera will reduce the total amount of light hitting the blue camera. Since the camera has a certain amount oi spurious noise which it generates even under conditions of no light, the light reduction imposed by the filter will cause a reduction of the signal-to-noise ratio at the camera output.

The method of color scansion embraced by one form of the present invention consists of the following steps. We shall consider a three primary color system. The scene is scanned by two cameras fixed to represent diierent primary color aspects of the scene being scanned. A third primary color representation is produced by scanning the scene with an ordinary black and white or panchromatic camera having no one particular color sensitivity. All colors are represented equally by this camera. The signal produced by this camera is then a typical black and white type television signal. This black and white or panchromatic signal is then subtractively combined with the sum of the signals produced by the two other cameras. rIhe resulting signal will then represent the diierence between the sum of the colors represented by the two single-color cameras and white light. By deiinition then, the resultant signal must be a primary color signal. For example, if the two single-color cameras represented red and green aspects of the picture, the resultant signal produced by the present invention would represent the blue aspects of the scene.

i The overall signal-to-noise ratio of the resulting color television signals will be improved because the panchromatic camera has no light reducing filter in front of it.

The present invention, then, takes further advantage of the fact that picture detail in a reproduced television image is produced by high frequency signal components. Thus, in order to prevent the effects of misregistration of these high frequency components as produced by the separate color cameras, the present invention, by means of lters, reduces the high frequency output of the two single color cameras. The frequency components of the black and white camera 5 are, however, not altered. The high frequency components produced by the black and white Y camera may. be further added to the output of the other two single color cameras to replace that detail which was cut oif by the filters. Consee.v quently, no matter how the resulting signals are used to produce a color television imagefthe high"` frequency components in each color aspect image must register since the detailmin each color record` is produced by the single panchromatic camera. .15

A more complete understanding of the present invention, as well as other objects and eat-uresof advantage, will appear from the following defscription when taken in connection with the accompanying drawings.

In the drawing, Figure l is a block diagram representation of a color television scanning system utilizing the present invention.

Figure 2 is a block representation of another form of color television scanning system embodying the novel features ofthe present invention.

Figure 3 illustrates in blockform still another color television scanning system embodying'the novel features of theV present invention.

Turning now to Figure 1, there is shown at ill, I2 and I4 three separate color channel terminals.. for a color televisionsystem. Channel i@ is designated to feed the blue channel of the system. Channels I2 and I4, however, correspond to the 35 green and red channels of the system. The ool"` ors blue, green and red, ofcourse, are additive Y primary colors whosesum will'produce white light. Channels I0,I2 and I4 are respectivelyv fed by mixer circuits I6, I8 and 2U. To get the l0 proper color signals to appear at the output of the mixer circuits, three television cameras 22, 24 and 26 are used.

Camera 22 maybe referred'to as a blue camera. It may comprise a television camera which is sensitive to substantially Yno color except blue. On the other hand, itmay 4comprise an ordinary black and white television camera `23having a blue filter 3U in front of it. Inanyevent, the signal "appearing at the output terminal 32 of 50 the camera 22 willrepresent intensity variations corresponding to the blue Vcolor component of the scene scanned by the camera. For'later'conveniencethe blue signal'has been" designated as BL-I-BH. BL ArepresentsV the low frequency components of the blue signal while BH represents the high frequency components'of the blue signal. The red camera 261s arranged in a similar manner to the blue camera 22.v It has, for example,V been shown as Ya-regular black and 60 white camera 34 arranged to look through a red iilter 36. The output of the-red camera appearing at terminal Sli-willthen-comprise'theredsignal -RL-ITRH. Againthesetwo components represent respectively the lowand'highfrequencyV 65 portions of the red signal. The outputs ofuthe blue and thered-camerasare, -of course, channeled to the inputsof the -mixersI-B and 2i! `which feed the terminals I and i4 of the color channels.

APrior art practicevwould-now lead one toernploy a third color camera constructed somewhat similar to the cameras vZand` 26.L This carriera,Y however, woule1 be madesensitive -to the-third l primary color being `used, namely` green: TheA 76 ingsbetween zeroA- and two megacycles.

4 output of the green camera would then be used to feed the mixer I8 and hence the channel I2. However, according to the present invention the camera 24 is nothing more than a black and white television camera. It preferably has light response which is panchromatic in nature. That is, it responds .substantially equally to all of the various colors .inthe scene at,whicl1it looks. The output of the panchromatic camera 24 is then applied by a low pass filter 4I) to the input of the mixer I8. Low pass lters 42 and 44 are also...placed..between the blue and red cameras and the respective mixers I6 and 20. The characteristics of the filters 4D, 42 and 44 are substantially 'theV same,V and, for example, are indicated as passing only those video signals fall- 'Ihe outputs of .the low pass filters 42 and 44 are applied to 'the input of the mixerl8 via the polarity re- 0 versal circuits 46 and 48. This means that into variety, there will be-appliedthree signals;v TheU rst signal will be the low frequency components of the blues andthesecond-signal will be-the These Y low frequency components :of the reds. twolow frequency components will'be ofthe same and red .lowffrequency components.l These will be fed into themixerWthoutgoingthrougha the mixer I8 represents; thefdifference between the sum .of twosoutlof.three=co1or.-components and a white. signal.; representing .allthree l.color components.

It will` be appreciated .that the. arrangement of the polarityreversers `IIGland Handmixer.. I8 may be A.altered in any` way. to produce the same function. They. maybefreplaced by any,-means for subtractively `combining, the., panchromatic camera. signal` with. the other twc. .color signals.,

to produce a resultant sigr1a1..

So far, the V.output of the mixer I8 represents only the low :frequencyjcomponents .of Aa .green color V television 1 signal.` Outputs of... Inixers;l .I 6

and 28 would also represent only low frequency components of theblue. and` red'` camera outputs. Thus, a reproduced television imagerbasedupon these signals alone wouldflackpicture '.detail.z.-.V

According to the presentr invention,y .the high frequency components Puoi the` panchromatic signalproduced by-thecarnera 24 are separated by means of the. high pass filteren. The high pass lter ilallowsyeiective` passage of signals from 2 to 4 megacycles or higher.. In some cases those signals above4 megacycles areV cut oi later by the transmitter so that even though the lters pass frequenciesabove 4 megacycles the result is the same as though band pass filters were used. Four megacycles is an rarbitrary upper limit set for the convenience of describing thepresent system. The output of the high pass filter 50 is applied by a switch'52'to the inputs of thernixers I6, II)v and 20F Since the" panchromaticcamera 24 `represents-intensity*variations of all the col-k ors. the output of the high pass filter 50 will represent picture detail of all three color channels taken as a sum. Thus, the input to color channels I 0, I2 and I4 will be supplied by low frequency components of single color records of the scene and high frequency components from a. panchromatic scansion of the scene.

It is noted that the use of the panchromatic high frequency components on all three channels will produce acceptable color balance in the reproduced color television picture. This comes about by way of the fact that the human eye has limited ability to resolve ne detail when such detail resides in changes from one color to another of substantially the same brightness. This ability of the eye to resolve ne detail under such conditions is very much less than its ability to notice changes in brightness such as from black to white. This phenomenon is explained in greater detail in my U. S. Patent No. 2,554,693 filed December 7, 1946, and entitled Simultaneous Multi-Color Television.

Should it be desired tortake advantage of only the improved signal-to-noise ratio provided by the present invention and not realize the advantage of improved definition, the switch 52 may be opened and switches 54, 55 and 58 closed. This will bypass the low pass circuits 40, 42 and 44 so that the outputs of mixers I6 and 20 will contain both the low and high frequency components of their respective cameras. The use of mixers I6 and 20 and high pass circuit 50 under these conditions is not necessary since switch 52 is open.

A reduced band width transmission system of the type described in my above-mentioned U. S. Patent No. 2,554,693, is also possible with the present invention. With such an arrangement, low pass circuits 42 and 44 are left in effect as drawn in Figure 1. Low pass circuit 45 would be bypassed to let `both the panchromatic lows and highs (PL-l-PH) reach the mixer I8. The high pass circuit 5i! as well as mixers IE and 20 need not then be provided. The total transmission band -width of the system would then be 2 megacycles each for the blue and red cameras plus 4 megacycles for the green channel. This makes a total of 8 megacycles required for transmitting the composite color signal. As explained in my abovementioned U. S. patent, this represents quite a saving over the 12 megacycles otherwise necessary for a simultaneous color transmission system.

-The arrangement in Figure 2 embodies about the same principles as Figure l. Figure 2, however, indicates the application of the system of Figure 1 to a field sequential type color television system. Three color cameras 22a, 24a and 25a produce the required blue signal, panchromatic signal and red signal. Low pass filters 42a and 44a have been put in series with the blue and red camera outputs. These low pass filter circuits, as previously described, feed the mixers IBa and 2da. respectively. In Figure 2 some simplification over Figure 1 has been made. The low pass filter 40 connected with the output of the panchromatic camera 24 in Figure 1 has been omitted. Under such circumstances, the output of the high pass filter 5ta in Figure 2 is applied only to the inputs of the mixers Ilia and a. Polarity reversers 46a and 48a connecting the outputs of the low pass filter circuits 42a and 44a with the inputof the mixer I8a are shown for the reasons indicated in connection with Figure 1. The signals appearing at the output terminals Ilia, Iza and Mat of the mixers I'Ga, I8a and 20a are of the sameV character as described with respect to Figure 1.

As stated, Figure 2 illustrates a field sequential type color television system. Thus, the outputs of the mixers Ilia, [8a and zllamay be fed to the inputs of gate tubes 60, 62 and 64. These gate tubes are normally biased to cutoff by means of the positive bias supplied to their cathodes. However, a 20 cycle per second generator 66 synchronized by the generator 68 is arranged to key the i gate tubes on successively. This is accomplished through the well known use of the phase shifter 'l0 and the 240 phase shifter l2. These phase Shifters could be in the form of delay lines or networks. Gate tube 64 will first turn on. Then 64 will close and tube 62 will turn on. After tube 62 has closed, tube 6U will become conductive and the cycle will repeat itself. The interval between successive conduction of tubes could, of course, be 1%@ of a second, as is required by the present-day television standards. Thus, across the output of resistor 'it there will appear during successive intervals of /GO of a second first red channel information, then green channel information and nally blue channel information. This, of course, may be fed to a transmitter 'I6 for radio transmission. Camera deflection circuits 78 have been indicated in Figure 2 by way of example. Further information on the field sequential system of transmitting color television images may be obtained through reference to U. S. Patent No. 2,389,039 to A. N. Goldsmith entitled Color Television System.

The arrangement of Figure 3 shows the present invention applied to a dot sequential type color television system. A detailed understanding of such a color television system may be had through reference to the issue of the RCA Review for December 1949, pages 504-524 in an article entitled A 6 megacycle compatible high definition color television system by the RCA Laboratories Division, Princeton, New Jersey. Here again, a blue camera 22h, a panchromatic camera 24h and a red camera 26h are provided. The outputs of these cameras are connected to low pass filters 42h, 40h and 44h respectively as in Figure 1. The outputs of the low pass circuits 42h and 44h are connected through polarity reversers 4Gb and 48h to the input of the mixer` Ib, also as in Figure l. However, for the purposes of the dot sequential system of color transmission, no high frequency components from the panchromatic camera are inserted into the mixer Ib as was shown in Figures 1 and 2. Instead, the high frequency components of the panchromatic camera output are passed through the high pass circuit 50h to the input of another mixer 89. The mixer Bil combines the high frequency components passed by high pass circuit 59h with the output of a signal commutator circuit or sampler diagrammatically indicated at 82. The sampler 82 isillustrated in a very functional manner. It is shown to consist of a rotating armature 84 which rotates in the direction of the arrow tosuccessively contact the terminals 86, 88 and 99 of the sampler. The output of the sampler is taken from the armature 84 and applied to the mixer 80. The speed at which the armature 84 thus samples the red low frequency components, the green low frequency cornponents and the blue low frequency components is determined by some form of comuiutator drive circuit indicated at 92. Although indicated as being of a mechanical nature, the sampler S2 with its drive circuit 92 `may take a variety of electronic forms. For example, the use of gate tubes as in Figure 2 may be employed. However, the sampling rate of the dot sequential system in Figure 3 is much higher than the field sequential. system of .aThisfis: descsibedffiin fulliidetailiini the aboyereferencedll articleg.appearingfini thefgRCA RerieW-i: l Hcweverrby waypfsexamplewit; may-be borne in:-.rnind.ethat;f,the sampling rateiof the system.ff Figure;;3 .is pref erably-in the y neighbor-V hoodgof several megacycles or so ,-foreacli Acolor;- The--output aofethe.4 mixer :BQ vsavillythenv constituteV Y erartakenain@combination with two vrnonocrorna-tic` typecameras,` other color-response characteristics maya bewused without-departing froinfthefspiritand scopefof-thepresent invention. Forexample;

iniFigure l, theI camera22qmay begiven a reclgreen-;response so that its output atfterminalfSZV willicomprise Aboth red and green signal information; In'order to getthe green-signal alone-for application to `terminal I2 of Eigure 1,it will then beconlygnecessary to lsubtract the-output of-vthe red camera 26 -from :the red-greenl output of the mQdied-:Camera .-221` Under ysuch conditions the blue s-ignalmay be obtained'byfmerely subtracting the=.output of modied-camera 22 (R4-Gl from the output oftheipanchromatic camera 24. Many combinations are possible but as will be seen-from the-above discussion f-.theffmorecolors to which each camera is'responsivegthe,greater Awill be the signale to snose.: f ratio ,of. f the resulting composite televisionlsignal;

Byway `ofa still' further example, the panchromatic; camera lshown in the ,above embodiments-may,` be.,replace d by ia camera responsive only tozftwo-colors; The other two cameras may bezgiven other Asuite-lille:response characteristics, each again responsive to buttwo colors. Thus, in Figure -1 Vcamera 22 .may be givenv-red-green responser (R+-G), camerazZa red-blueresponse (R+B),- while'carneraqZ vrmay giVe-blue-green (B-l-G) response;-V Under y such conditions theY output ofi-the reci-green camera couldV .be subvention can be seen to be quitelarge.-

It is thus-:seen that the present invention nds ;g.

application .to a variety of color-television sys-1.

tenis.v Its advantages can-be realizedfiinanyi-f` system where'color representation -of an object-` is to bernade by v`television-scanning techniques;

Having thus described -my- --inventiom what 4VI claim-is:V

1. In a'colcrtelevision system, a first television*- V camera-responsive to `substantially none but one:Y

primary'color aspect of a television scene to produceya colorsignal, a second television cameraresponsive to substantially all color aspects of thesame television 'scene to produce a substantially panchromatic type television signal, means including yanv electrical signal subtracting circuit "0 inputs for subtractively combining electricaljsiga'- having a signalinverter anda plurality of signal nals and delivering a resultant toan output terminal, connectionsapplying the color signalV cute- Y puts yofl said Atelevision cameras` to .respectively different inputs of said subtracting circuit rthe signais each representing .a dilerent complemen-V tary-v fco1oraspect `of the scene.. scannedifa rst" scanning means responsive to light oftsubstan-f ond scanning means zresponsiveto f substantially none butfvonescolori aspect of ,the l color scenesto develcppa colorsignal train, a signal subtracting means having a pluralityof input;circuits;and`

at least .one output circuit,meansfiorapplying thesaid panchromatic signal train and said color signalf train ,tothe inputs of saidsubtracting means whereby the resultant signal train appear-1: ing in the nutputcircuit of said subtractivemeans representsa color; aspect of saidscene, which is complementary to the` signal train developed by f saidsecond scanning means.

3. `In an electrical systemic-r scanning `a ,color 1 scene to Aproduce separate trains ofv electrical signals :each lrepresentinga ,different complementary color aspect of the scene scanned, a rst scanning means responsive to light. of 'substantially. .all, colors emanating frornsaid sceney to Y develop a panchromatic typesignaltraini a second Y scanning means rresponsive -to substantially none but one color aspectopthefeolor sceneto develop a color signal ,train,;a f third scanning means Vrespcnsiveto substantially none but Voneother color aspect of the color scene different from that color represented by said second scanning means to develop another color signal train, means `for sub-k tractivelycombining said panchromatic signal. train with each of saidcolor trains to produce t.

resultant; signal trains, f means for combining in an additive manner said resultant signal-trains into a single remaindersignaL-train Vwhereby said remainder signalftrain represents Aa--color` aspect of. saidi scene which is *complementaryl to the coloraspects represented by said second and third scanning means.-

4. Anelectricalscanning vvsystem for representing in color .the eXploredare-as `of. a scene vby `a plurality ci concomitantly generated, signal trains, each'trainrepresenting adiierent complementary color recordof the scene, a panchro- `matic scanningl means fcrscanningsaid. scene to' develop` a panchroinatic signaltrain representing intensity variations ci Vsubstantially all component colors in the scene,V a plurality of other scanning. ymeans vfor` scanning said scene, each. Yof said .other scanning means developing a'. color signal trainsubstantially representing intensity variations of a different single component color 'in the scene,lmeans for additively combining all of vsaidcolor signaltrans produced by said other scanning meansto form a result,-

ant signal, and means for subtractively -combingsaidpanchroinatic signal train with said resultant signal whereby to produce a difference:

signal train which is representative of intensity `vari-ations off a-color component in said scene different :froiabut complementary. to said 'colorcoinponents'developed by said plurality of :other scanning means.

5; An electrical scanning system for `represent- :ingin-'coloritheexploredfareas of--a scene by anent color in the scene, a mixing circuit connected with said scanning means for subtractively combining said panchromatic signal train with each of the colorsignal trains developed by said other scanning means to produce a resultant` signal whereby said resultant signal represents intensity variations of a color component in said scene different from that represented by any of said plurality of other scanning means.

6. Apparatus according to claim 4 wherein there is additionally provided a low pass filter connected between the output of said panchromatic scanning means and said subtractive combining means, a separate low pass iilter similar to said first mentioned low pass iilter connected between the output of each of said other scanning means and the input of said subtractive combining means, a high pass filter adapted to cutoff at a frequency not substantially less than the highest frequency effectively passed by any of said low pass filters, connections coupling the input of said high pass lter to the output of said panchromatic scanning means, a signal mixing circuit in the output of at least one of the other scanning means and on the output side of its respective low-pass iilter, and means for coupling the output of said high pass filter to the input of said signal mixing circuit.

`'7. Apparatus according to claim 6 wherein there is provided a plurality of additional separate signal mixing circuits each having one of their inputs connected with the output of a diflferent one of said other scanning means and connections from the output of said high pass filter to another input on each of said additional mixing circuits whereby the outputs of each of said additional mixing circuits represent the sum of both low frequency signal components of signal trains corresponding to different single color y components in the scene plus the high frequency components of the signal train developed by said panchromatic scanning means.

8. An electrical scanning system for representing in` color the explored areas of a scene by a plurality of concomitantly generated signal trains each train representing a different complementary color record of the scene, a panchromatic scanning means for scanning said scene to develop a panchromatic signal train representing intensityv variations of substantially all component colors in the scene, a plurality of other scanning means for scanning said scene, each of said other scanning means developing a color signal train substantially representing intensity variations of a different single component color in the scene, means for combining in the same polarity all of said color signal trains to form a resultant signal, and means for combining said resultant signal with said panchroznatic signal train. in opposite polarity relation whereby to produce a diierence signal train which is representative of intensity variations of a color component in saidscene dierent from but complementary to said color components represented by said plurality of other scanning means.

9. An electrical scanning system for representing in color the explored areas of a scene by a plurality of concomitantly generated signal trains each train representing a different complementary color record of the scene, comprising a panchromatic scanning means for scanning said scene to develop a panchromatic signal train representing intensity variations of substantially all component colors in the scene, a plurality of other scanning means for scanning said scene, each `of said other scanning means developing a color signal train substantially representing intensity variations of a diiTerent single component color in the scene, a mixing circuit including signal polarity reversing circuits connected with the output of said scanning means for combining the signal trains developed by said other scanning means in opposite polarity relation with said panchromatic signal train to produce a resultant output signal having components representing intensity variations of a color component in said scene different from that represented by any of said plurality of other scanning means.

1Q. Apparatus according to claim 9 wherein there is additionally provided a separate low pass filter connected between the output of each of said other scanning means and the input of said mixing circuit whereby high frequency components of said mixing circuit resultant output signal represent panchromatic intensity variation information while low frequency components of said output signal represent single color intensity variation information.

11.` Apparatus according to claim 10` wherein there is additionally provided a plurality of additional mixing circuits each having input circuits and output circuit connections from each of the outputs ofl a plurality of said low pass lters to an input circuit of a separate and respective one `of said' additional mixing circuits, a high pass filter adapted to cutoff at a frequency not substantiallyless than the highest frequency effectively passed by said low pass filters, a connection between the input of the high pass iilter and the panchromatic scanning means and a connection from the output of said high pass lter to another input circuit on each of said additional mixing circuitswhereby the outputs of said additional mixing circuits represent the sum of both low frequency signal components of signal trains corresponding to'respectively different single color component in the scene plus the high frequency A components of the signal train developed by said panchromatic scanning means.

12. In a `color television system a irst television i `camera channel `representing virtuallyI all the color aspects of a given scene to produce a substantially panchromatic type television signal, a

plurality of other television camera channels each representing substantially none but one primary color aspect of the given scene to produce a color signal, a mixing `circuit connected with all of said television channels for combining all of said color Signals in opposite polarity relation with said panchromatic signal to produce a resultant output signal having components representing color aspects of the given scene different from those represented by any of said other television carnera channels, a signal sampling circuit having a A plurality of inputterrninals which are successively, individually and periodically channeled to a single output terminal at a predetermined isampling'frate vato produce anI .outputrsi'gnalzfcomprising a series of grouped information elements,

itospass l.only high frequency panchromaticisignal l"components, andi means forsmixing` the', Youtput of;A said: high. passfflter withi the outputrcfreach ,Y of isaidlow pass lters before; theiitssaid'con- Anection to said sampling circuit.

'13;y Apparatus .according to :claim lzlfwherein ..said :color televisionisystem'isbased onthreegpri- .mary colorsyredagreen and blue yand Whereinzthet number Aoii said.pluralityzofsotheir:cameraxchannelsis two; eachfrepresenting' va diierentrzone of .1;said primary colors.

felt-'rin afcolon rtelevisioIr-:systenr a'r rstrtftele- .-Vision ca-mera:I channel representing lvirtuailyzall the color` aspects of a given scenerto'flproduce a fsubstantiallyf panchromatic'ityperftelevision sig nal,` aapluralitywof-.lother television #camera channels-V each representing: substantially.. none but .one:primarycolor-aspect :of the-givennscene to Y produce accion-signal, afmixing .circuit connected -f with allwof-said televisionchannels for combining tionywith=said lpanchromatic signalytoproduce a resultant Aoutput ysignal: havingfcomponentsrepresenting color .aspectsofxthe'.lgivenxscenediffer- `entfronnl those representednbyf any 'of iisaid other :etelevisionccamera VV:cl'xannelsn aasignal :.'fsampling iici-rcuit .chai/ing` ai plurality :fof-.l inputifterrninals which ,aref successively;individuallytandfiperiodically 'channeled to a single'. outputfterrninalfat a predetermined samplingratestorxproduce': an :outputsignalcomprising afseries ot'groupedinorma- Ytiorrelements;:each elementin a given-.group representing signal informationfffappearing.vatfadifferent @input terminal, aesep-arate flow. passlter A'connected between a `.signal output of teach 'of .said

Yother camera :channels-and a1dierentf-frespec- `tiveinput*terminal of i-said r sampling; circuit; a connection. 'fromf-the output;y otrsaidffmixing l. circuit tand fanotherrseparate" inputfterr'ninal 'ofsaid f sampling.circuit,V a high :pass i'ilte'r fhayingzitsfin- .putteonnec-ted'with 'the outputof saidcitsttele- .yision'carnera channelto-.pass-onlyiiglilfrequency panch-roulatie-signal.v components;andcmeansftf or the output of saidsigna'l sampling' circuit.

, a 215. Inan electricalgsystenforzsoanningacolor to-developa' iirstyideolsignal vtrain; awsecond scanning means atfleast responsive 'to light "of a colori to :whichr .said .rsti scanning ,means v is -re 65 lsponsivefsai@secondi-scanning meansdeVeIOping a= second -video signalftrain, a .signalv subtracting rneans'having a plurality of: input circuits andzat Y.416.-.Apparatus.'V accordingl-.to-aclaim lawlierein 12 f there fiscadditionallyiprovdedtwoL low:v passt elec- .itricalilters and'zone highrpass:,electricalilter, fzandaconnectionszplacing:respective low passlter .series betweenzthe outputsfof saidrscanning; means '5I/,and saidLsubtraoting means input circuits .and "wherein tadditionalzzmeans areprovded for.;con necting .theinput of said high pass lter with the -foutputzor atileastione of said scanningmeans 'and Ameans@fon-mixing"the output. of said Yhighzpass N :lterwith the output of said subtracting. means.

.$117. Amelectricalfscanning system orfrepre- :'senting; in'co'lor, the explored areas vof a-scene 'i 'byv a: plurality `of iconcornitantly."generated signal ',-trainsJeachfrepresenting a differentV one of aplu- 15. rality-liof.fr rel'atedvcolor records; of f. the scene;v said .systems comprisingtrin combination, av rsti. scan- :uiingi'meansxtfor' scanning-saidl scene :to: develop :L a1rst Videozisignal train representing kintensity f Vvariations* of ai plurality of: the related rcolorsieml.braced byisaidxlcolorrecords, a pluralityxofuother '.seanning means .forscanning said'scenegzeach of '1 fothepfscanningtmeansdeveloping a discrete zauxiliarylyideo signalttrain representingfcolorin- ':tensitycvarationsffof a typenotN represented'by 29:5 :any'other-lzsingle 'scanning 1in-Jans,l means forialgei In"oraicz'illy:conbining?said' rstfvideoi'zsignal train `Withsatl.least-:one :ofzsaid auxiliaryxsignal" trains -zto'produce ardierence signalv trainrepresenting color" intensity wariations y'noizfalonerepresented 30 by any siiigle-scanningmeans.

; `1t. Apparatus accordingto'claim?173wherein j there: -isiadditonallynprovided rrneansifor further combining rsignal' trains 'other thanlsaid rsttsigi nal tra-in atozproducefother fsignalftrains .repre- 3D sentingu single;.":coloririntensity :.ivariationsfm lotlflerwise produced or alone n'epresented'fbyfany singlesca'nningfmeans.

a .19T In a :colorrtelevision system arstitelevision camera channel efprodu'cing' a .iirst lsignal :repre- 40' `senting .latfl'east two color 'aspects' of a' givenscene, aa second'ltelevision'icamera; channelproduc-ing a Y second;sigrial'representing''atl'least 'one :color raspeet :of Isaidtgiven scene, afthird: television 'camera :ichanielpru'ducing aithird signal representing at v.leastw one color';'\aspect 'offsaid `given scene; apluvrality: oflter:J meansffonselecting the flow' frelquencyportions ofzcertan of said signals,- and A:combining-fmeans'for combining 'said low V'frequencyselected.portionso1.said certain signals 0 `Witlr any remaining'noneselected color. aspect signals'ftof obtain atleast; .three video' signals lwhich .video'signals'representiat 'least the' low frequency portions of a singledierentcolor aspect ofsaid r'given="scene,meansLfor transmitting each of said 55. last-:namedsignalsrand meansfor lselecting and :transmitting the high-frequency `components of said? `:firstsign'al 1 along with said- -last-nam'ed low :'-freqnencycnideo signals.

lReferences Citedin the file ofA this' patent -UNITEDQ STATES PATENTS Number Name Date ...2,173,490 u Yanes 'Sept. .19, 1939 V 2,493,200 Lande "Jan, 3,1950 2,554,693 .Bedford ons M'ay"29; 1951 FOREIGN PATENTS H Number Country EDate 0 `5in-,.443 Great Britain Aug; '1, .1940

` OTHER REFERENCES A ...sixemegacycle compatible.. highedefinition `color.,-.television systemffvRCA. Review-VOL 10, T5..-DeC --.19l9 pages 1-5. 

